R语言gsub替换字符工具的具体使用

gsub()可以用于字段的删减、增补、替换和切割,可以处理一个字段也可以处理由字段组成的向量。

具体的使用方法为:gsub("目标字符", "替换字符", 对象)

在gsub函数中,任何字段处理都由将“替换字符”替换到“目标字符”这一流程中实现,令替换字符为''''可实现删除,令替换字符为"目标字符+增补内容"可实现增补,替换和切割也是使用类似的操作。

> text <- "AbcdEfgh . Ijkl MNM"

> gsub("Efg", "AAA", text) #将Efg改为AAA,区分大小写

[1] "AbcdAAAh . Ijkl MNM"

 任何符号,包括空格、Tab和换行都是可以识别的

> gsub(" I", "i", text) #可识别空格

[1] "AbcdEfgh .ijkl MNM"

同时字符可以识别多个,进行批量置换

> gsub("M", "N", text)

[1] "AbcdEfgh . Ijkl NNN"

除此之外,gsub还有其他批量操作的方法

> gsub("^.* ", "a", text) #开头直到最后一个空格结束替换成a

[1] "aMNM"

> gsub("^.* I(j).*$", "\\1", text) #只保留一个j

[1] "j"

> gsub(" .*$", "b", text) #第一个空格直达结尾替换成b

[1] "AbcdEfghb"

> gsub("\\.", "\\+", text) #句号.和加号+是特殊的,要添加\\来识别

[1] "AbcdEfgh + Ijkl MNM"

SyntaxDescription
\\dDigit, 0,1,2 ... 9
\\DNot Digit
\\sSpace
\\SNot Space
\\wWord
\\WNot Word
\\tTab
\\nNew line
^Beginning of the string
$End of the string
\Escape special characters, e.g. \\ is "\", \+ is "+"
|Alternation match. e.g. /(e|d)n/ matches "en" and "dn"
Any character, except \n or line terminator
[ab]a or b
[^ab]Any character except a and b
[0-9]All Digit
[A-Z]All uppercase A to Z letters
[a-z]All lowercase a to z letters
[A-z]All Uppercase and lowercase a to z letters
i+i at least one time
i*i zero or more times
i?i zero or 1 time
i{n}i occurs n times in sequence
i{n1,n2}i occurs n1 - n2 times in sequence
i{n1,n2}?non greedy match, see above example
i{n,}i occures >= n times
[:alnum:]Alphanumeric characters: [:alpha:] and [:digit:]
[:alpha:]Alphabetic characters: [:lower:] and [:upper:]
[:blank:]Blank characters: e.g. space, tab
[:cntrl:]Control characters
[:digit:]Digits: 0 1 2 3 4 5 6 7 8 9
[:graph:]Graphical characters: [:alnum:] and [:punct:]
[:lower:]Lower-case letters in the current locale
[:print:]Printable characters: [:alnum:], [:punct:] and space
[:punct:]Punctuation character: ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
[:space:]Space characters: tab, newline, vertical tab, form feed, carriage return, space
[:upper:]Upper-case letters in the current locale
[:xdigit:]Hexadecimal digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f

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